Retinal ganglion cells connect in highly ordered patterns to the central visual nuclei. This study will elucidate possible developmental mechanisms which result in these orderly patterns of neuronal connections in the visual system. There are three major lines of investigation. First, morphogenesis of the optic chiasm will be investigated to evaluate the mechanical guidance as a possbile mechanism for directing axonal growth. Particular attention will be given to morphological changes in the chiasm that may allow formation of an ipsilateral retinofugal projection. Second, the pattern of ganglion cell genesis, ganglion cell cytomorphic maturation, and retinotectal synaptogenesis will be characterized and compared. This is to evaluate temporal gradients of maturation as a mechanism responsible for neuronal specificity by correlating parallel maturation gradients in the retina and central visual nuclei with the actual synaptogenic sequence between the retina and these nuclei. And third, cell death will be examined in the developing visual system as a mechanism for the removal of neurons projecting out of the proper pattern. The timing of ganglion cell death will be compared to the timing of the loss of the aberrant ipsilateral retinorectal projection during normal development to determine if this is a viable mechanism for the elimination of this projection.